int  getResult( char word[] ){
    int count[30]={0};
    while(*word!='\0'){
        count[(*word)-'a']++;
        word++;
    }
    int min=(1<<31)-1;
    int max=(1<<31);
    for(int i=0;i<26;i++){
        if(!count[i])continue;
        if(count[i]>max)max=count[i];
        if(count[i]<min)min=count[i];
     }
    int tmp=isPrime(max-min);
    return tmp?max-min:-1;
}